An automotive agricultural machine, such as a combine, field chopper, or the like, frequently has a speed-control element--the so-called throttle--which is constituted as a lever pivotal about a horizontal axis normally at floor level and provided on its free upper end with a horizontal handle extending parallel to the lever pivot axis. Normally this lever is provided immediately ahead and to the right of the operator seat and next to the steering wheel, so the machine operator can easily reach it with his or her right hand to set or reset the machine ground speed. The lever holds in any set position, and normally is pushed forward to increase ground speed and pulled back to decrease it or stop so that there is some logical relationship between the motion of the control element and the response of the controlled function.
In addition to the operator's duties of steering the machine and establishing ground speed, he or she must be ready to raise or lower the intake to compensate for changes in terrain. It is furthermore necessary to occasionally reverse the intake device as well as the cutter drum if something, such as a piece of wood or wild animal, that could itself be hurt or that could damage the machine gets caught in the machine.
Obviously the controls for these various functions must be as convenient as possible to the operator. Even in the best systems, however, there is an often unacceptably long reaction time before they can be operated, and it is even fairly common that the wrong control is operated in an emergency.